Pixel-Wise Noise Reduction in Thermal Images

1. A method comprising: receiving an image frame comprising a plurality of pixels arranged in a plurality of rows and columns, wherein the pixels comprise thermal image data associated with a scene and noise introduced by an infrared imaging device; and processing the image frame to determine a plurality of non-uniformity correction (NUC) terms to reduce at least a portion of the noise, wherein each NUC term is associated with a corresponding one of the pixels and is determined based on relative relationships between the corresponding one of the pixels and associated neighborhood pixels within a selected distance from the corresponding one of the pixels, wherein the processing comprises: for each pixel of the image frame, comparing the pixel to each of its associated neighborhood pixels, for each comparison, adjusting a first counter if the pixel has a value greater than the compared neighborhood pixel, for each comparison, adjusting a second counter if the pixel has a value less than the compared neighborhood pixel, and selectively updating the NUC term associated with the pixel based on the first and second counters.

2. The method of claim 1 , further comprising, for each comparison, adjusting a third counter if the pixel has a value equal to the compared neighborhood pixel, wherein the updating is also based on the third counter.

3. A method comprising: receiving an image frame comprising a plurality of pixels arranged in a plurality of rows and columns, wherein the pixels comprise thermal image data associated with a scene and noise introduced by an infrared imaging device; and processing the image frame to determine a plurality of non-uniformity correction (NUC) terms to reduce at least a portion of the noise, wherein each NUC term is associated with a corresponding one of the pixels and is determined based on relative relationships between the corresponding one of the pixels and associated neighborhood pixels within a selected distance from the corresponding one of the pixels, wherein the processing comprises: for each pixel of the image frame, comparing the pixel to each of its associated neighborhood pixels, for each comparison, adjusting a counter in a first manner if the pixel has a value greater than the compared neighborhood pixel or a second manner if the pixel has a value less than the compared neighborhood pixel, and selectively updating the NUC term associated with the pixel based on the counter.

4. The method of claim 1 , wherein the associated neighborhood pixels comprise at least one pixel in a different column and a different row than the corresponding one of the pixels.

5. The method of claim 1 , wherein the distance is a first distance, wherein the portion of the noise is a first portion, the method further comprising repeating the processing using a second distance to update the NUC terms to reduce at least a second portion of the noise.

6. The method of claim 1 , wherein the noise comprises spatially uncorrelated fixed pattern noise (FPN) and spatially correlated FPN.

7. The method of claim 1 , further comprising applying the NUC terms to the image frame to remove the portion of the noise.

8. The method of claim 1 , further comprising temporally damping the NUC terms.

9. The method of claim 1 , further comprising weighting the NUC terms based on gradients between the pixels.

10. The method of claim 1 , further comprising: processing the image frame to determine a plurality of spatially correlated fixed pattern noise (FPN) terms to reduce a portion of the noise comprising spatially correlated FPN associated with rows or columns of infrared sensors of the infrared imaging device; and applying the spatially correlated FPN terms to the image frame before the NUC terms are determined.

11. The method of claim 1 , wherein the image frame is an intentionally blurred image frame, wherein the thermal image data is blurred thermal image data.

12. A system comprising: a memory component adapted to receive an image frame comprising a plurality of pixels arranged in a plurality of rows and columns, wherein the pixels comprise thermal image data associated with a scene and noise introduced by an infrared imaging device; and a processor adapted to execute instructions to process the image frame to determine a plurality of non-uniformity correction (NUC) terms to reduce at least a portion of the noise, wherein each NUC term is associated with a corresponding one of the pixels and is determined based on relative relationships between the corresponding one of the pixels and associated neighborhood pixels within a selected distance from the corresponding one of the pixels, wherein the instructions to process the image frame are adapted to cause the processor to: for each pixel of the image frame, compare the pixel to each of its associated neighborhood pixels, for each comparison, adjust a first counter if the pixel has a value greater than the compared neighborhood pixel, for each comparison, adjust a second counter if the pixel has a value less than the compared neighborhood pixel, and selectively update the NUC term associated with the pixel based on the first and second counters.

13. The system of claim 12 , wherein: the processor is adapted to execute instructions to, for each comparison, adjust a third counter if the pixel has a value equal to the compared neighborhood pixel; and the instructions to update the NUC term are adapted to cause the processor to selectively update the NUC term also based on the third counter.

14. A system comprising: a memory component adapted to receive an image frame comprising a plurality of pixels arranged in a plurality of rows and columns, wherein the pixels comprise thermal image data associated with a scene and noise introduced by an infrared imaging device; and a processor adapted to execute instructions to process the image frame to determine a plurality of non-uniformity correction (NUC) terms to reduce at least a portion of the noise, wherein each NUC term is associated with a corresponding one of the pixels and is determined based on relative relationships between the corresponding one of the pixels and associated neighborhood pixels within a selected distance from the corresponding one of the pixels, wherein the instructions to process the image frame are adapted to cause the processor to: for each pixel of the image frame, compare the pixel to each of its associated neighborhood pixels, for each comparison, adjust a counter in a first manner if the pixel has a value greater than the compared neighborhood pixel or a second manner if the pixel has a value less than the compared neighborhood pixel, and selectively update the NUC term associated with the pixel based on the counter.

15. The system of claim 12 , wherein the associated neighborhood pixels comprise at least one pixel in a different column and a different row than the corresponding one of the pixels.

16. The system of claim 12 , wherein the distance is a first distance, wherein the portion of the noise is a first portion, wherein the processor is adapted to execute instructions to repeat the process using a second distance to update the NUC terms to reduce at least a second portion of the noise.

17. The system of claim 12 , wherein the noise comprises spatially uncorrelated fixed pattern noise (FPN) and spatially correlated FPN.

18. The system of claim 12 , wherein the processor is adapted to execute instructions to apply the NUC terms to the image frame to remove the portion of the noise.

19. The system of claim 12 , wherein the processor is adapted to execute instructions to temporally damp the NUC terms.

20. The system of claim 12 , wherein the processor is adapted to execute instructions to weight the NUC terms based on gradients between the pixels.

21. The system of claim 12 , wherein the processor is adapted to execute instructions to: process the image frame to determine a plurality of spatially correlated fixed pattern noise (FPN) terms to reduce a portion of the noise comprising spatially correlated FPN associated with rows or columns of infrared sensors of the infrared imaging device; and apply the spatially correlated FPN terms to the image frame before the NUC terms are determined.

22. The system of claim 12 , wherein the image frame is an intentionally blurred image frame, wherein the thermal image data is blurred thermal image data.

23. The system of claim 12 , further comprising a focal plane array (FPA) adapted to provide the image frame, wherein the FPA comprises an array of microbolometers adapted to receive a bias voltage selected from a range of approximately 0.2 to approximately 0.7 volts.